Methylchloroform (1,1,1-trichloroethane) may be produced by Friedel-Crafts catalyzed reactions such as the liquid phase hydrochlorination of vinylidene chloride using a ferric chloride catalyst. The methylchloroform product exiting from the reactor contains a portion of the catalyst which subsequently promotes decomposition upon moderate heating when purification techniques such as distillation are attempted.
It is conventional to conduct vinylidene chloride hydrochlorinations as continuous processes at temperatures of about 38.degree. C., using about 0.1 to 10.0 percent ferric chloride catalyst based on the weight of reaction media (reaction media is usually excess methylchloroform).
Principal contaminants in the reaction product are relatively volatile hydrogen chloride and vinylidene chloride together with non-volatile catalyst. All of these contaminants are readily separated from the methylchloroform product by distillative techniques. The distillative procedure is usually conducted in stages and in normal operations some small transfer of catalyst from stage to stage is experienced. In addition, unreacted hydrogen chloride contained in the product stream corrodes the distillation apparatus and tends to form a scale of metal salts which accumulate in the distilland with a deleterious destabilizing effect.